Ink jet recording apparatuses that record information by using the piezoelectric effect of a piezoelectric element have been known in the art.
An ink jet recording apparatus of this type includes an ink jet head, driving signal supply means, and relative movement means. The ink jet head includes a head assembly including nozzles and pressure chambers storing ink therein and communicated to the nozzles, and piezoelectric actuators for applying a pressure on the ink in the pressure chambers so as to discharge ink droplets through the nozzles by the piezoelectric effect of piezoelectric elements. The driving signal supply means supplies a driving signal to the piezoelectric actuators. The relative movement means relatively moves the ink jet head and recording paper with respect to each other while ink droplets are being discharged from the nozzles. While the ink jet head and the recording paper are being relatively moved with respect to each other by the relative movement means, the driving signal supply means supplies the driving signal. The piezoelectric actuators are activated by the driving signal to discharge ink droplets through the nozzles. The discharged ink droplets land on the recording paper to form ink dots. A large number of ink dots on the recording paper together form an intended image on the recording paper.
When recording an image with an ink jet head in which a plurality of nozzles are arranged in the secondary scanning direction Y (the direction perpendicular to the relative movement direction), the formed ink dots may vary from one another in the diameter thereof or the landing position thereof with respect to the secondary scanning direction Y, as illustrated in FIG. 28, due to a defect of the ink jet head, etc. In such a case, white streaks 101 extending in the primary scanning direction X (the relative movement direction) appear on the recording paper, thereby lowering the image quality.
In order to solve the problem, N-pass recording has been used in the art, in which the same line is scanned N times (N is a natural number equal to or greater than two) in the primary scanning direction X. As illustrated in FIG. 29, a 2-pass recording operation, for example, is performed by forming ink dots (solid-circle ink dots), skipping every other dot position, while the ink jet head is moved in the primary scanning direction X in the first pass (the first scan) and then forming ink dots (open-circle ink dots) to fill the skipped dot positions in the second pass (the second scan). The operation is performed so that the second uppermost ink dot formed in the first pass and the uppermost ink dot formed in the second pass are next to each other in the primary scanning direction X. In this way, it is possible to prevent white streaks extending in the primary scanning direction X from appearing on the recording paper.
However, N-pass recording lowers the recording speed because of the need to scan the same line N times.